Coastal regions are the epitome of multisector and multiscale interactions among human and natural systems. Coastal states represent over 80% of U.S. gross domestic product (GDP) and near-coastal regions feature densely populated urban centers, a diverse range and concentration of economic activities, and a wide array of critical infrastructure (stormwater, wastewater, transportation, electricity, etc.). The natural system features in coastal zones, from coastal hydrology and shoreline morphology to environmental systems and services, create amenities that are a primary driver of coastal development. These regions are also subject to a wide range of natural and human system hazards, including floods, droughts, heatwaves, technology advances, or market dynamics, many of which are changing or becoming more pronounced. Understanding the nature of these changing stressors, the non-linear dynamics, and the cascading effects within the integrated coast is a scientific grand challenge that requires capabilities and expertise that spans multiple agencies and missions. To that end, the interagency Coastal Integrated Hydro-Terrestrial Modeling (C-IHTM) Coordinating Group of the U.S. Global Change Research Program and the Multisector Dynamics (MSD) research community convened to discuss the cross-cutting and interdisciplinary nature of coupled human-natural system coastal modeling challenges, specifically focusing on open science and the enabling tools; potential cross-cutting region and topic specific use cases; integrated modeling frameworks to enable coupled coastal human-natural system interactions; and bridging coastal communities of practice, including research to operations and back to research. This talk will address the scientific grand challenge drawing from this interdisciplinary workshop and relevant ongoing coastal research activities, including the DOE Integrated Coastal Modeling (ICoM) project.